Coalescence and Film Formation from Latexes

By Kenneth L. Hoy

A paint is a complex liquid coating material composed of pigments, fillers, polymeric binders, and other additives dispersed and/or dissolved in a liquid. When applied to a surface, the liquid is changed by a film forming process to a solid, adherent composite film.

The formation of a paint film is so spontaneous and familiar that most give little thought to the mechanism and dynamics of the process. Yet it is the dynamics of film formation that can provide perspective to the design and application of polymeric latexes. Previously, a number of workers have studied the “mechanism” by which the latex particles coalesce with each other.1-5

Their attention has been focused on the details of how particle-particle contacts and interactions take place. It is the author’s intent to emphasize the thermodynamics of the filming process. A general theory of film formation from a paint is derived from thermodynamic considerations.

Model calculations are made and the results are encouraging. They are able to predict the effect of pigmentation and identify new areas for polymer and formulation research. The theory is capable of being specialized for either solvent or latex systems.